LONDON, Jan 2 (Reuters) - Iranian police arrested 100 protesters in the capital on Monday, the deputy governor of Tehran said, as a police crackdown intensified against anti-government demonstrations that began last week.

Security forces have struggled to contain protests that broke out last Thursday and have continued nationwide in the boldest challenge in years to the country’s clerical leadership.

The unrest is the worst since crowds took to the streets in 2009 to condemn the re-election of then-president Mahmoud Ahmadinejad. One member of the security forces was reported killed on Monday.

“200 people were arrested on Saturday, 150 people on Sunday and around 100 people on Monday,” Ali Asghar Naserbakht, deputy governor of Tehran province, was quoted as saying by semi-official ILNA news agency on Tuesday.

Hundreds of others have been arrested in other cities.

He said the situation in Tehran was under control and the police has not asked for the help of the Revolutionary Guards special forces.

Mehr news agency also quoted a judiciary official as saying that several ringleaders of protests in Karaj, the fourth largest city in Iran, have been arrested.

Videos on social media on Monday showed an intense clash in the central town of Qahderijan between security forces and protesters who were trying to occupy a police station, which was partially set ablaze.

There were unconfirmed reports of several casualties among demonstrators.

The government said it was temporarily restricting access to the Telegram messaging app and Instagram. There were reports that internet mobile access was blocked in some areas. (Editing by Matthew Mpoke Bigg)